1. Field
Apparatuses consistent with exemplary embodiments relate to a lead frame and a semiconductor package including the lead frame.
2. Description of the Related Art
A lead frame for a semiconductor package is a main component of the semiconductor package, together with a semiconductor die. The lead frame is used to support the semiconductor die and serves as a lead for connecting the semiconductor package to an external device.
FIG. 1 is a schematic plane view of a general lead frame 1, and FIG. 2 is a schematic cross-sectional view of an example of the general lead frame 1 according to the related art. Referring to FIG. 1, the general lead frame 1 includes a plurality of lead units 20 and a die pad unit 10. A semiconductor package is manufactured in such a way that a semiconductor die is attached to the die pad unit 10 of the general lead frame 1, and the semiconductor die and each of the lead units 20 are connected to each other via a wire, and then, are molded by using an epoxy molding compound (EMC), or the like.
Since these days lead (Pb) is not used in a semiconductor packaging process, a palladium pre-plated frame (PPF) type lead frame is widely used. However, a plated layer of the PPF has a hard material property, and thus, is not easily bonded to a bonding wire formed of copper (Cu). To solve this problem, gold (Au) having a relatively soft material property may be plated on a surface of the PPF. However, due to the price of gold (Au), cost thereof may increase.
Due to this problem of the PPF, the lead frame 1 in which a nickel layer 60, a palladium layer 70, a silver layer 80, and a gold layer 90 are sequentially plated with a base material 50 formed of Cu may be used, as illustrated in FIG. 2. The silver layer 80 of the lead frame 1 is formed relatively thick and has a soft material property and thus may be easily bonded to a Cu wire formed of a hard material.
However, when a semiconductor package, that is manufactured using the lead frame 1 of FIG. 2, is used in a high-temperature and humidity-absorbing environment, due to migration of silver atoms, a short between the lead units 20 or a short between the lead unit 20 and the die pad unit 10 occurs so that the lifespan and performance of the semiconductor package may be decreased.
FIG. 3A is a schematic cross-sectional view of another example of a lead frame 2 according to the related art, and FIG. 3B is a photo showing epoxy bleeding that occurs in a die attaching process.
In order to solve the problem, as illustrated in FIG. 3A, the lead frame 2 having roughness on its surface, on which a roughly-plated layer 62, a palladium layer 72, and a gold layer 92 are sequentially stacked on a base material 50 formed of Cu, may be used. The roughly-plated layer 62 may be formed by rapidly electroplating metal, such as nickel or Cu, by using a high current.
The lead frame 2 illustrated in FIG. 3A has roughness on its surface, and thus, has a large contact area with a Cu wire, Thus, the lead frame 2 has an excellent bonding property with respect to the Cu wire.
The lead frame 2 of FIG. 3A has an excellent bonding property with respect to the Cu wire but has an outermost layer formed of Au, and thus, a surface area of the outermost layer is large. Thus, bleeding of an epoxy adhesive may occur in a die attaching process. FIG. 3B illustrates a wire bonding region of the lead frame 2 of FIG. 3A. Referring to FIG. 3B, bleeding of the epoxy adhesive occurs widely in the wire bonding region of the lead frame 2.
Due to the bleeding of the epoxy adhesive, the lead frame 2 of FIG. 3A may lower the reliability of the semiconductor package in spite of having an excellent bonding property with respect to the Cu wire.